1. Field
This application relates to heating systems, specifically heating systems that work through the use of steam.
2. Prior Art
Steam heating systems are one of the common types of central heating systems used in residential, commercial, and industrial buildings. The operating principle involves heating water in a boiler to produce steam pressure. The steam rises through a network of pipes, and into hollow metal radiators. In order to allow the steam to fill the radiators, the air in the system must be displaced to make room for the incoming steam. Each radiator thus has an air vent, usually located on the opposite side of the radiator from which a steam supply pipe enters, that allows the air to be pushed out of the piping and radiator by the steam. Each air vent has a fixed size restrictive hole through which the air escapes, used to regulates the rate at which the air is allowed to be displaced, and therefore the rate at which the steam fills the radiator.
The radiators provide a great degree of surface area that helps the heat from the steam transfer to the radiator's metal. The heated radiator metal then transfers its heat to the ambient air in the various rooms of the building where they are located. As the energy from the steam is given up in the form of heat, it begins to condense back into water. The condensate water is directed back into the boiler from which it came, through either returning down the pipes from which it originated that are pitched back toward the boiler, or through a system of condensate pipes that separate the condensate water from the new, hot steam that is coming from the boiler.
The even distribution of heat throughout a building is controlled by the rate at which air is allowed to be displaced out of each radiator. This is accomplished through the use of air vents, such as the one described in U.S. Pat. No. 2,494,293 to Gorton, 1950 Jan. 10. Each vent bears a differing sized air escape orifice identified by a system of letters and numbers. The sizing of each radiator's air vent is based on a number of criteria, such as their proximity to the room containing the thermostat, the floor the radiator is located on, and how much piping is between each radiator and the boiler. The theory is that an appropriately sized air vent is chosen so that the steam will arrive at and heat each radiator at about the same time. After much of the air has been expelled from the piping and radiator(s) and the radiator(s) begin to heat up, the air vent is caused to close by any number of factors, depending on the vent's design, such as temperature and/or moisture/condensate build-up. Once an air vent valve closes, no more steam can enter into that radiator, and it ceases to rise in temperature.
The steam, trapped in each radiator, begins to lose its temperature as its heat is transferred to the metal of the radiator, and, in turn, to the surrounding air in which the radiator is located. The steam cools, condenses back into water, and returns back to the boiler through the piping. For a reversal of the same reasons that acted upon the air vent to make it close, the valve opens. This allows for more steam from the boiler and piping to push out any new air that has entered the system, and new, hot incoming steam to fill the radiators again.
This process continues until the room where the thermostat is located has increased in temperature sufficiently to open the thermostat's internal limit switch, breaking the boiler's circuit, causing the boiler to turn off. When the temperature again drops below the thermostat's set temperature, the thermostat's internal switch again closes, turning the boiler back on, repeating the process.